The engineer hired to build Gus Fring’s underground laboratory is Werner Ziegler.
Werner leads a team of German construction workers hired to create the hidden superlab beneath an industrial laundry. The project takes place during the fourth season and requires strict secrecy, complicated logistics, and Mike Ehrmantraut’s supervision.
Werner becomes homesick and eventually escapes the workers’ compound to see his wife. His unauthorized trip threatens Gus’s secrecy and leads Mike to track him down. Mike ultimately kills Werner to prevent him from exposing the project.
Werner is sometimes confused with Kai Wexler, another German worker on the construction crew. Kai is disruptive and impulsive, while Werner is the project’s lead engineer. The completed laboratory later becomes associated with Gus’s methamphetamine operation in Breaking Bad.